1. Field of the Invention
The present invention relates to a manual adjustment mechanism for adjusting the position of various components in a vehicle.
2. Description of the Prior Art
Adjustment mechanisms are widely used in automotive vehicles for adjusting the position of a variety of components such as reclining seat backs, articulating seat cushions, head restraints, seat tracks, window panes, and the like. Many of such adjustment mechanisms commonly comprise a ratchet, or drive gear, operatively connected to a pawl, or sector gear, for selectively adjusting the position of the component connected to the pawl. These adjustment mechanism, however, have a limited range of adjustability and positioning as dictated by the range of movement between the drive gear and sector gear.
Other adjustment mechanisms include a cylindrical drum coupled to the component for positioning the component in response to infinitely adjustable rotation of the drum. A spring is generally coiled around the drum for applying a circumferential friction force on the outer cylindrical surface of the drum to prevent the rotation thereof when the adjustment mechanism is in a non-actuated position. A control device is commonly connected to the coiled spring for releasing the coiled spring from the drum to allow rotation of the drum, and therefore, positioning of the component. An example of a drum and coiled spring adjustment mechanism is illustrated in U.S. Pat. No. 5,163,736. The ""736 patent discloses an adjustment mechanism for controlling the inclined position of a seat back relative to a seat cushion for an automotive seat assembly. A cylindrical drum is rotatably coupled between the seat cushion and the seat back for providing rotational movement of the seat back. A spring is coiled about the cylindrical drum and includes a first free end coupled to the seat cushion and a second free end coupled to a control arm. The control arm engages the second free end to coil, or compress, the spring around the drum create a frictional force therebetween to prevent the rotational movement of the seat back. The control arm also unwinds, or releases the compression of the spring coiled about the drum to allow rotation of the drum and seat back between a plurality of inclined positions. However, the adjustment mechanism fails to include a locking device coupled between the drum and the spring to compress the spring around the drum in response to incidental rotation of the seat back relative to the seat cushion. That is, incidental load forces on the seat back may result in xe2x80x9cback drivingxe2x80x9d of the drum by overcoming the frictional forces between the spring and the drum.
Therefore, it is desirable to provide a manual adjustment mechanism for adjusting the relative position of the component while preventing incidental back driving of the component against the adjustment mechanism.
Accordingly, the present invention relates to a manual adjustment mechanism for adjusting a relative position of a component with a vehicle. The mechanism comprises a support bracket, an input shaft rotatably supported by the support bracket for providing rotary input to adjust the component, and an output shaft operatively coupled to the input shaft and rotatably supported by the support bracket for providing rotary output to adjust the component and for receiving rotary input from the component. The mechanism further includes a housing fixedly secured to the support bracket and having a tubular inner surface. A coupler is disposed within the housing and operatively coupled between the input shaft and the output shaft for transferring the rotary input of the input shaft to the rotary output of the output shaft. The coupler has a pair of spaced apart tube walls. The mechanism also includes a coiled spring seated between the housing and the coupler and compressed against the inner surface of the housing. The coiled spring has at least one tangential distal end disposed between the tube walls. A control device is mounted to the input shaft for rotating the coupler into engagement with the distal end of the coiled spring to release the spring from the inner surface and transfer the rotary input from the input shaft to the rotary output in the output shaft. The mechanism additionally includes a cam driver rotatably disposed within the coupler for engaging the distal end of the coiled spring in response to the rotary input of the output shaft to compress the coiled spring against the inner surface of the housing and prevent further rotation of the output shaft and the input shaft.